Everett, Wash.-based fusion startup Helion announced Friday that it has reached a key milestone in its quest for fusion energy. The plasma inside the company’s prototype Polaris reactor has reached 150 million degrees Celsius, three-quarters of the way to what the company thinks it will need to run a commercial fusion power plant.
“We’re obviously really excited to get to this point,” David Kirtley, co-founder and CEO of Helion, told TechCrunch.
Polaris also works with deuterium-tritium fuel — a mixture of two isotopes of hydrogen — making Helion the first fusion company to do so, according to Kirtley. “We were able to see the fusion power increase dramatically, as expected, in the form of heat,” he said.
The startup is locked in a race with several other companies trying to commercialize fusion power, a potentially limitless source of clean energy.
This potential has investors rushing to bet on the technology. This week, Inertia Enterprises announced a $450 million Series A round that included Bessemer and GV. In January, Type One Energy told TechCrunch it was in the process of raising $250 million, while last summer Commonwealth Fusion Systems raised $863 million from investors including Google and Nvidia. Helion itself raised $425 million last year from a group that included Sam Altman, Mithril, Lightspeed and SoftBank.
While most other fusion startups are targeting the early 2030s to deliver electricity to the grid, Helion has a contract with Microsoft to sell electricity starting in 2028, though that power would come from a larger commercial reactor called Orion that the company is currently building, not Polaris.
Each fusion launch has its own milestones based on the design of its reactor. Commonwealth Fusion Systems, for example, needs to heat its plasmas to more than 100 million degrees C inside its tokamak, a doughnut-shaped device that uses powerful magnets to contain the plasma.
Techcrunch event
Boston, MA
|
June 23, 2026
Helion’s reactor is different, it needs plasmas that are about twice as hot to work as intended.
The company’s reactor design is called a reverse field configuration. The inner chamber looks like an hourglass and at the wide ends the fuel is injected and turned into plasma. The magnets then accelerate the plasma towards themselves. When they first fuse, they are around 10 million to 20 million degrees C. Powerful magnets then compress the fused sphere further, raising the temperature to 150 million degrees C. This all happens in less than a millisecond.
Instead of harvesting energy from fusion reactions in the form of heat, Helion uses the fusion reaction’s own magnetic field to generate electricity. Each pulse will push back on the reactor’s own magnets and induce an electrical current that can be harvested. By getting electricity directly from fusion reactions, the company hopes to be more efficient than its competitors.
Over the past year, Kirtley said Helion has perfected some of the circuitry in the reactor to increase the amount of electricity they recover.
While the company uses deuterium-tritium fuel today, it plans to use deuterium-helium-3 in the future. Most fusion companies plan to use deuterium-tritium and capture the energy as heat. Helion’s fuel, deuterium-helium-3, produces more charged particles that push strongly against the magnetic fields that confine the plasma, making it better suited to Helion’s approach to direct electricity generation.
Helion’s ultimate goal is to produce plasma reaching 200 million degrees C, far higher than other companies’ goals, depending on reactor design and fuel selection. “We believe that at 200 million degrees you get into the optimal sweet spot where you want to run a power plant,” Kirtley said.
Asked if Helion had reached a scientific tipping point — the point at which a fusion reaction generates more energy than is needed to start it — Kirtley hesitated. “We’re focused on electricity, electricity generation, rather than purely scientific milestones.”
Helium-3 is common on the Moon, but not here on Earth, so Helion has to make its own fuel. To begin with, they fuse deuterium nuclei together to produce the first batches. While in normal operation deuterium-helium-3 fusion will be the main source of energy, some of the reactions will still be deuterium-on-deuterium, producing helium-3 that the company will purify and reuse.
Work is already underway to refine the fuel cycle. “It was a pleasant surprise in that many of these technologies were simpler than we might have expected,” Kirtley said. Helion was able to produce helium-3 “with very high efficiency, both in terms of throughput and purity,” he added.
While Helion is currently the only fusion startup using helium-3 as fuel, Kirtley said he thinks there will be other companies in the future and indicated he would be willing to sell it to them. “Other people — once they come in and recognize that they want this direct electricity recovery approach and see how it increases efficiency — they’re going to want to use helium-3 fuel as well,” he said.
In addition to the Polaris experiments, Helion is also building Orion, the 50-megawatt fusion reactor it needs to fulfill its contract with Microsoft “Our ultimate goal is not to build and deliver Polaris,” Kirtley said. “This is a step on the way to scaled-down power plants.”